Approximately how many Jews were killed in the September 11 terrorist
attacks?  I ask because I live in a Middle Eastern country where many
people believe 9/11 was carried out by Israeli agents and that the
Jews working in the Twin Towers were warned not to go to work that
day.  I find this not only ridiculous but patently offensive. 
However, I have been unable, using Google searches for "religion
victims September 11, "Jewish victims 9/11," "Jews died 9/11," etc. to
find any statistics on religion of victims.  Your assistance will
advance the cause of international compassion.

I certainly agree with you that this rumor is ridiculous and
offensive. I have gathered some material which refutes the allegation.

It is estimated that between 400 and 500 Jews died in the attacks on
the World Trade Center on 9/11. The exact number is not known, since
official record-keeping does not list the religions of the victims.

"While no one knows for certain how many Jews were killed on Sept. 11,
the most reliable estimates put the number at about 400. This despite
the blasphemy spread in the Arab world that no Jews perished, having
been warned by the Mossad agents who supposedly carried out the
attacks."

The Jewish Week
http://www.thejewishweek.com/bottom/specialcontent.php3?artid=362 

"A senior Jewish journalist friend called me before the first
anniversary of 9/11 and said to me: 'You have to do something about
the Arab concept that the Jews are responsible for 9/11. Can you find
out how many Jews were killed there?'

A week later I called him and said 'about 500,' which is 15 to 17
percent of all the victims killed in the World Trade Center. The
figure would have been even higher had it not been for the fact that
many Orthodox Jews went to work an hour later because of the Selichot
prayers recited in the days before the Jewish New Year."

Jerusalem Center for Public Affairs
http://www.jcpa.org/phas/phas-13.htm

Here are two excellent articles which debunk the widely-spread story
alleging that thousands of Jews stayed home on September 11th because
they had been warned in advance of the attack:

Snopes: Rumors
http://www.snopes.com/rumors/israel.htm

Slate: 4,000 Jews, 1 Lie
http://slate.msn.com/id/116813

It is possible that some who wish to believe that 9/11 was an Israeli
conspiracy will not accept all of the reference sources listed above.
If that is the case, the plainest evidence that many Jews died in the
World Trade Center is the list of the names of the dead:

"How many Jews actually died in the world Trade Center attacks is not
known with any precision. The official New York City 'Missing Persons
List' does not categorize victims by their religion or nationality.
But ask families with names like Adler, Aron, Berger, Bernstein,
Cohen, Eichler, Eisenberg, Feinberg, Friedlander, Goldstein,
Greenstein, Horwitz, Jablonski, Kestenbaum, Kirchbaum, Kleinberg,
Levi, Levine, Mayer, Rosenberg, Rosenblum, Rosenthal, Sachs,
Safronoff, Schwartz, Shulman, Shwartzstein, Silverstein, Solomon,
Steinman, Temple, Weil, Weinberg, Weingard, Weinstein, Weiss, Zukelman
what they wouldn't give to see their loved ones again. Why didn't they
get a conspiratorial cell-phone message warning them to stay home? By
all appearances, the 9-11 hijackers were equal-opportunity murderers."

WorldNetDaily
http://www.worldnetdaily.com/news/article.asp?ARTICLE_ID=35516

Here you will find the full list of names:

9-11 Heroes
http://www.9-11heroes.us/victims-world-trade-center.php

My strategy in locating this information consisted of many Google
searches, using various combinations of keyphrases such as "jews
killed," "jews died," "jewish victims," "on 9/11," "september 11,"
"world trade center," "wtc," and "twin towers."

I hope this will be useful to you. If anything is unclear, please
request clarification; I will be glad to offer further assistance
before you rate my answer.

Best regards,
pinkfreud

Thank you, Pinkfreud-ga, for an excellent job.  You were both savvy
and thorough.  I will be using this material more than I wish I had
to, I'm sure.